This invention relates to electrical connectors of the type which include reflowable solder elements, and in particular to such connectors having improved means for retaining the solder elements in place and to methods for forming such connectors.
A wide variety of modern electrical connectors and pins include a mass or preform of solder mounted on or adjacent to the pin. After the connector or pin is mounted in place, the solder is melted in a reflow operation in order to form a solder joint. Several approaches have been used to position the mass of solder in place prior to the reflow operation.
One approach is to retain the solder directly on the pin, as for example by crimping the pin around the solder, crimping the solder on the pin, or utilizing a solder or other bond between the pin and the solder. The following U.S. patents illustrate this approach: Lynch U.S. Pat. No. 3,864,014; Lynch U.S. Pat. No. 3,905,665; Cobaugh U.S. Pat. No. 3,978,569; White U.S. Pat. No. 3,997,237; Schell U.S. Pat. No. 4,019,803; Seidler U.S. Pat. No. 4,120,558; Seidler U.S. Pat. No. 4,203,648; Mackay U.S. Pat. No. 4,500,149; Seidler U.S. Pat. No. 4,592,617; and Seidler U.S. Pat. No. 4,679,889.
A second approach is to retain solder preforms on a plate or strip that extends over several pins and is moved along the axes of the pins to position the solder preforms on the pins. See Lane U.S. Pat. No. 3,184,830; Phohofsky U.S. Pat. No. 3,214,827; Pardee U.S. Pat. No. 3,591,922; Reid U.S. Pat. No. 4,216,350; and Proceedings of the 11th Electrical Insulation Conference pp. 242-245 (IEEE Publ. 73CHO-777-3EI, 1973).
A third approach is simply to slide solder preforms along the pins of a connector before the connector is mounted in place. See Harris U.S. Pat. No. 3,462,540; Lynch U.S. Pat. No. 3,932,934; Reavill U.S. Pat. No. 4,206,542; Swiss Pat. No. 653,838; and The Western Electric Engineer, Vol. 19, No. 2, (1975). As shown in Lynch '934, retention strips or protrusions on the pins may be used to prevent the solder preforms from sliding off of the pins.
A fourth approach is to hold the mass of solder in the connector housing adjacent the pins. See Hartman U.S. Pat. Nos. 4,641,426 and 4,663,815; Faile U.S. Pat. No. 1,188,055; Ellis U.S. Pat. No. 3,525,799; and Document S/M-139 of Alphametals, Inc. (1979). The Hartman patents disclose reservoirs formed in the connector housing to retain solder masses around the connector pins.
Two problems often associated with solder preforms on connectors relate to retention and reflow of the solder preform. Solder itself is an alloy with virtually no memory or spring properties. For this reason, there is little tendency for a solder preform to retain itself on a connector pin. Of course, if a solder preform falls off of a connector pin, the result is an unacceptable failure to form a proper solder connection.
The second problem is related to the reflow operation. Typically, the insulator body of the connector tends to shield the solder preform from infrared light used to heat the solder to reflow temperatures in infrared soldering systems. For this reason, the insulating housing may prevent or retard the solder preform from reaching the temperature needed.
A need presently exists for an improved electrical connector that positively retains a solder preform in place in the connector housing and prevents the solder preform from falling out of position prior to the reflow operation. The present invention is directed to such an improved electrical connector, and to methods for making such a connector.